Attack on the uncastled king: rook to a5 (a1·9)
c9-26705naming tag (square·N)Opens in the app if installed, otherwise downloads the APK.
The tactical motive
Chess960 twist: use the unusual starting setup of the pieces.
Uncastled king: the enemy king is stuck in the centre — punish it before it castles.
Winning tactic: there is a move that gains a decisive advantage — find it.
Difficulty 1200 ShuffleRating — club-player level.
White to move — find the best continuation
How to recognize this tactic
In Chess960 the pieces start on unfamiliar squares, so tactics appear earlier and from unusual angles. Do not trust classical patterns — read the actual lines of the bishops, the rooks and the queen from where they really stand in this position.
An uncastled king in the centre is a standing target. Look for ways to open the central files and diagonals against it with checks and threats before it can shelter — every tempo the king spends in the middle is a chance for a combination.
This position hides a concrete tactic that wins material or mates. Start with the most forcing candidate moves — checks, captures and threats — and calculate each to a clear end before choosing; the winning line is usually the one the opponent cannot meet.
General method: before you move, list the forcing candidates — every check, every capture, every direct threat — and calculate those first. The solution to a tactic is almost always among them.
Position on the board
White: king b1, rook a1 d1, bishop b3 f4, knight g1 e3, pawn b2 c2 d2 e2 f3.
Black: king c8, queen a5, rook a8 d8, bishop f6 e8, pawn g5 a6 d6 e6 c7 f7 h7.
12 white and 13 black pieces are on the board; the puzzle position arises after move 15.
The position in numbers
Black are ahead by 5 points of material (27 against 32; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on b1, the black king on c8.
It is White to move on move 15, with 29 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 5 pawns, Black 7. No file is fully open, so the heavy pieces have to be pried in. Half-open for White: a, g, h.
The White king has 1 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
15. Rxa5 gxf4 16. Ng4 Bg7 17. Nh3 c5 18. Nxf4
Why it works
- Great move! rook to a5 keeps the pressure (+3.5).
- knight to g4 develops smoothly.
- A natural move: knight to h3.
- Best move. knight to f4 is exactly what the engine plays (+3.9).
- You win a piece — the queen.
- If instead gxf4, then Ng4 and you win the queen.
Move by move
- 15. Rxa5 — rook to a5 (capture)
- gxf4 — pawn to f4 (capture)
- 16. Ng4 — knight to g4
- Bg7 — bishop to g7
- 17. Nh3 — knight to h3
- c5 — pawn to c5
- 18. Nxf4 — knight to f4 (capture)
Types in this puzzle
Winning blow
Find the strike that wins material by force.
A winning blow is a forced material gain that does not fit a single textbook motif. The general tactical recipe applies: spot loose pieces, an awkwardly placed king, overloaded lines. Go through the forcing moves in order of violence — checks, captures, threats — because most combinations start with one of them. Do not judge by feel: calculate the concrete line until the outcome is beyond doubt.
Only move
Everything else loses — find the only move that holds.
An only move is a position where everything loses except one single continuation. You cannot play "by hand" here: run through fundamentally different defenses — run away, block, trade, counterattack — and discard the ones that fail. The hallmark of these puzzles is that the obvious moves lose quickly while the solution often looks strange. First understand exactly what the threat is — then the one saving move reveals itself.
Counter-strike
Don't defend — answer the threat with a bigger one.
The counter-strike: instead of defending against the threat, you answer with a bigger threat of your own. While your opponent grabs a pawn, you deliver mate — the arithmetic favors you. Look for a counter when direct defenses fail: do you have a check, an attack on the queen, a mating threat? The beginner's error is meeting every threat with a reflexive defense without checking the counterattacking resources first.
About this position
These pieces come from starting position #891.
SP-891 · BastionGuard — King shifted to c or f, knights kept clear of the edges — 168 positions in all.
The king starts on c1, the rooks on a1 and d1, the queen on b1.
The king already stands on c1, so castling long moves only the rook, from a1 to d1.
A bishop starts in the corner on h1: it has a single diagonal, which the g-pawn unlocks, running out to a8.
Every pawn on the second rank is defended from the very first move.
The setup belongs to the BastionGuard family; read right to left it becomes position 65.
The engine's main line opens with g3.
Morozov Balance Index: 2 of 100 — class D — largest edge. Engine evaluation of the starting position: +53 centipawns for White (depth 41, 400 000 000 nodes).
Explore position #891Provenance
Mined from the project's engine self-play games.
Pack 008 · SP-891
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